Short communicationFootscan pressure insoles: Accuracy and reliability of force and pressure measurements in running
Introduction
Advancements in microcomputer technology have enabled manufacturers to develop in-shoe devices that provide measurements of plantar forces and pressures at the shoe-foot interface [1]. Like many brands of pressure insole, the Footscan® system is constructed with evenly distributed sensor cells. Each cell consists of a piezo-electric crystal and is an independent force measuring device. The sum of this force is equivalent to the total force applied to the body [2] and should equal the vertical force vector if measured simultaneously with a force plate. Because of the cell measurement of force, this technology can calculate plantar pressure based on the measured vertical load and the cell area [3]. For pressure insoles to be used a realistic and reliable measurement of plantar forces and pressures should be provided, yet despite its use in research [4], the accuracy and reliability of this system is not known. This investigation aims to provide this information.
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Method
Four female (23.5 ± 2.5 yr, 72.0 ± 2.2 kg) and four male (24.5 ± 1 yr, 87.3 ± 2.3 kg) participants were recruited to test two pairs of pressure insoles (females wore pair 1, sizes UK5-6; males wore pair 2, sizes UK9-10) (RSscan International, Belgium, 500 Hz). In-shoe temperature was measured at a consistent 36.5 °C throughout all trials.
Participants performed 16 running trials (3.81 m/s ± 5%). For each acceptable trial, participants contacted a force plate (AMTI, 500 Hz) without adjusting their normal gait, so
Results
When the data from each insole and participant were combined, ICC coefficients were 0.75 or greater. ICC values of 0.5–0.74 were also observed for much of the data when separated into the insole pairs and when the data for each pair were separated into the left and right insole. Peak pressure measurements at metatarsal one and three (right insole of pair 1), metatarsal two (left insole of pair 2 and pair 2 combined) and peak impact force (left insole of pair 2), was less than 0.5 (Table 1).
The
Discussion
In comparison to published standards (r > 0.75) [5], the combined data from the left and right step from two different pairs of insoles indicated excellent reliability for all measured parameters. Good to excellent reliability was generally observed for both pairs of insoles and for both the left and right insole in each pair, yet for selected single insoles and anatomical areas, poor reliability was observed. This has also been shown previously although not at the same locations as those in the
Conflict of interest statement
There is no conflict of interest with any other parties.
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